ABPIs calculated from CW Doppler and PPG ankle pressure measurements. The PPG signals were analysed both by visual judgement and by a software based, automatic algorithm.

Main results

The mean difference between ABPIs calculated from CW Doppler recordings and PPG (visual analysis) was −0.01 (limits of agreement (±two standard deviations) +0.16 to −0.19). The correlation coefficient was 0.93. When the algorithm was used, the mean difference (CW Doppler−PPG) was 0.05 (limits of agreement 0.28 to −0.18, r=0.89).

Conclusions

The PPG method is a promising technique with an inherent potential for automatisation of the ankle pressure measurements, thereby reducing the observer-dependency in ABPI recordings.

Jönsson, Björn

Abstract [en]

The first part of this thesis consists of a population-based epidemiological study on symptomatic leg arterial disease in a Swedish community, based on a postal questionnaire and systolic ankle pressure measurements, with calculation of the ankle-brachial pressure index (ABPI; usually ≥ 1.0 in healthy subjects). The second part investigates alternative methods for ankle systolic pressure measurements, with the potential of automation.

(Papers I-III) A postal questionnaire on leg symptoms and concomitant diseases was distributed to all the inhabitants of Vadstena 50-89 years old (n=7,524). The response rate was 92% and of those reporting any leg pain, 80% (353/441) attended an examination with ABPI determination. Symptomatic leg ischaemia (SLI) was defined as leg pain on walking + ABPI ≤ 0.8. The prevalence was 4.1 %, increasing with age, with no major difference between men and women. Other manifestations of arteriosclerotic disease (previous angina pectoris, myocardial infarction or cerebrovascular incident), hypertension and diabetes mellitus were more prevalent among SLI cases than in healthy subjects. At a four-year follow-up, the age and sex adjusted mortality ratio was almost doubled in SLI subjects. Their relative risk of a myocardial infarction, cardiac death and death due to any cardiovascular event was 2.7, 2.0 and 1.9, respectively, compared to an age and sex matched control group. In SLI subjects without a previous history of ischaemic heart disease, the relative risk of a myocardial infarction was 3.1. Cardiovascular disease alone was mainly responsible for the increased risk of death. At a ten-year follow-up, a baseline ABPI up to 0.8 was inversely correlated with mortality. In a Cox regression model, a low ABPI was significantly and independently associated with an increased risk of death. An ABPI of 0.81-0.99 was not associated with an increased mortality risk. Over ten years, 1/7 of the SLI cases had a leg vascular reconstructive procedure, the majority within the first two years, and 1/14 underwent a major amputation. In conclusion, in spite of the good prognosis of the local disease, SLI can be looked upon as a marker for generalised arteriosclerotic disease and as a risk predictor for severe arteriosclerotic events and premature death.

(Papers IV-VI) Oscillometric technique, commonly used for automatic arm blood pressure measurements, was validated against the CW Doppler in systolic ankle pressure determination in healthy subjects and in patients with leg arterial disease. While performing adequately in healthy subjects, it was found to be invalid in leg arterial disease. The oscillometric technique was deemed as not suitable for use as an automatic ankle pressure recorder in the diagnosis ofleg arteriosclerotic disease.

A new technique, based on a two-channel photoplethysmographic (PPG) probe (880nm) placed underneath the pneumatic cuff, together with electronics, was developed and compared with both CW Doppler and intra-arterial recordings in subjects without vascular disease, and with the CW Doppler in leg arterial disease. On visual analysis of the PPG curves, the agreement was good. An automatic algorithm for analysis of PPG-data gave comparable results. The PPG method is a promising technique for future automation of systolic ankle pressure measurements, and for inclusion in a complete ABPI recorder.